Telephone system



Dec. 29, 1925. 1,567,256

r 1 c. B; FOWLER I TELEPHONE SYSTEM Filed August 27, 1923 5 Sheets-Sheet 1 Marginal n z Q Q &- I 2'' 1 WW Dec. 29, 1925. H 1,567,256

C. B. FOWLER TELEPHONE SYSTEM Fil d August 1923 5 sheets-shes? 5 Mme/fian- Care/me 5. fw/a J W 40 4/77 Dec. 29,1925. 1,567,256

C. B. FOWLER TELEPHONE SYSTEM Filed August 27, 1923 5 Sheets-Sheet 4 &

Dec. 29, 1925.

C. B. FOWLER TELEPHONE SYSTEM Filed August 27, 1923 5 Sheets-Sheet 5 Patented Dec. 29, 1825..

warren Siam ra'rsu'r s Wade CLARENCEB. FQVILER, OF NEVI' Y'URK, N. Ya,- AQSIGNGR T WESTERN ELECTRIC COMPANY, INCORPORATED, 0F NEW YGBK, N. Y., A CORPQRATION 615 NEW TELEPHGNE sYsrni/r.

Application filed August 27, 1923. serial. No. 659',509.

To all /5011?) it filmy cancer n Be it known that l, CLARENCE B. F OWLER, a citizen of the United States of America, residing at New; York city, in the county of New York and State of New York, have invented certain new and useful lmprove= merits in Telephone SYS'CQITIS, of which the following is atull, clear, concise, and exact description. y

This invention relates to telephone systems and more particularly to operators equip ment einp'l oyedin connection with machine switcl'iing telephone systems,

In systems of the above mentioned type, an operator at a central oliice is required to handle various types oi connections, the most common beii'i-g local and toll switching connections. The establislni'ient of a connection over a local switching trunk requires a different condition of the dialing equipment than that required in establishing a toll switching connection; that is, the puls in' relay of a local trunk is generally sup plled with battery from the trunk circuit whereas the pulsing relay of a toll switching trunk receives battery from the dialing eqi' ipnient.

it is Object of this invention to enable i l 1 I L an operator to establish various types of connections over trunk circuits having different electrical characteristics by employing the least possible apparatus and with the least possible delay and confusion.

This object is attained in accordance with a feature oi this invention by' the provision of auniversal cord circuit wherein a marginal relay is employed to discriminate between local and toll switching trunks to mechanical offices, to condition an associated dial circuit for operation with either of said trunks. V

i'irn'other feature resides in thecontrol ot si lz naling means by a called subscriber to indicate to an operator that she has failed to restore the dial key subsequent to the establishment of a connection. The desirability of such an arrangement is readily seen when it is understood that the operation oi the dial key splits the talking circuit so that should a called party respond when the dial lif. wa sstill operated there would be no path tor the transmission otvoice currents and conversation between the called and calling parties would be impossible.

other faturs in be readily discernible from the following descriptions made with reference to the accompanying drawings wherein, 7

Fig. 1 shows a cord circuit F en'ibedying features of this invention and adapted to co operate with either a magneto line or a com- H1011 battery line.

Fig. 2 shows an operators telephone and dialing circuit. Q

Fig. 3 shows a local trunk circuit which may be employed 'to automatically extend aconnection to the common battery station.

Fig. 4; shows a toll switching trunl: which maybe employed to automatically extend a toll connection to a sujbsc-rib'er"s station.

Fig 5 shows a subscribers station and automatic switches by which a connection is extended theretotrom the toll switching trunk circuit of Fig.

The automatic switches have been shown schematically and only that part of the associated operating equipment which is necessary for a complete understanding of the in venti'onhas been disclosed in detail.

A call will first be traced from a calling subscriber on tllQCOJ-TIIHOII battery station A to the subscribers station P by way of the local trunk In order to trace through this connection Fig. 3 should be placed to the right ofFig. 1 and Fig. 2 immediately above Fig. 1 7

The subscriber at A on initiating a call removes the receiver from the switchhook whereupon a circuit is established for line relay 10 extending from grounded battery, through the right hand winding of relay 10, inner armature and backcontact of cutoff relay 11, over the subscribers line loop and apparatusat station A, back contact and outer armature of relay 11, to ground through the left hand winding of relay 10. Relay 10 operates in this circuit and establishes an obvious circuit for line lamp 12. 'lhe illumination of line lamp 12 indicates to the operator at the central oiiice that a call is awaiting her attention and she proceeds to answer it by inserting the answering plug 13 oi? the cord circuit F into jack 14 corresponding to the illuminated line lay 15, winding of relay l6, sleeve contacts of plug 13 and jack 14. to ground through the winding of relay 11. Relays 11, 16 and Ill 15 operate in this circuit. Relay 11 in operating disconnects the line relay from the conductors of the calling line thereby causing it to release and extinguish line lamp 12. Relay 16 in operating performs no useful function at this time. Relay in attracting its left hand and inner right hand ar1natures opens its normally closed contacts re moving the relay 17 and condenser 90 from in bridge of the left hand windings of re peating coil 19. This bridge is employed only in connection with calls originating at a magneto station. In closing the alternate contacts, the above mentioned armatnres of relay 15 connect ground and battery to the upper and lower left hand windings respec tively, of repeating coil 19, the battery being supplied by way of the winding of relay 18.

This battery is used for talking purposes.

Relay 18 operates in a circuit extending from grounded battery, Winding of relay 18, front contact and left hand armature of relay 15, lower left hand winding of repeating coil 19, ring conductor of cord F, lower normal contacts of ringing key 91, ring contacts of plug 13 and jack 1 1, over the subscribers line loop and apparatus atstation A, tip contacts of jack 14 and plug 13, upper normal contactsof ringing key 91, tip conductor of cord F, upper left handwinding of 1'8 peating coil 19, inner right hand armature and front contact of relay 15 to ground. Relay 18 operating 1n th1s circuit, prevents lamp 20 from illuminating at this time by connecting the battery 58 to the filament of lamp 20 which shunts out the battery nor mally associated therewith. At its outer right hand armature, relay 15 establishes a circuit which may be traced from grounded battery, filament of lamp 20, left hand winding of relay 21, to ground over the outer right hand armature and front contact of relay 15. Relay 21 operates in this circuit but lamp'20 does not as hereinbefore explained The ground connected to the alternate con tact and outer right hand armature of lay 15 also causes relays 22 and 23 to operate in a circuit extending from grounded. battery through the winding of relay 23, left hand winding of relay 22 to ground over the. outer right hand armature and front contact of relay 15. Relay 23 in attracting its armatures connects the condenser 24 between the left hand windings of repeating coil 19 thereby rendering the answering end of the cord serviceable for a common battery connection. Relay .22 in operating breaks the direct connection between the answering and calling ends of the cord and connects them through the repeating coil 19.

The actuation of talking key T as herein before mentioned connects the conductors 28 and 27 to the tip and ring conductors of eer/325s the answering end of the cord circuit and since these conductors are associated with the ope 'ators telephone set, by way of the normal contacts of relay 29, the operator is in a position to converse with the calling subscriber.

Upon learning that the desired party is located at substation P, the operator proceeds to reach the called subscribcrs station in the following manner :I-Iaving rc stored the talking key T, the operator tests for an idle local trunk, such as E. In making this busy test, the operator touches the tip of plug 30 to the sleeve of the trunk which, if busy, will be at battery potential, whereupon a circuit will be established extending from battery potential on the sleeve of the trunk, tip of plug 30, continuity contacts of relay 33, conductor 31 to ground through the winding of relay 32. :telay 32 operates in this circuit whereupon a circuit established extending from grounded battery, the winding of retardation coil 35, front contact and armature of relay 32, to ground through the right hand winding of repeating coil 36. The operators headset 99 is in series with the left hand winding of repeating coil 36 and induced current passing through this winding of coil 30, causes a click in her ear indicating to her that the trunk circuit is busy. If an idle trunk is tested, no battery will be present on the sleeve. Relay 32 will not be energized and the click in the headset 99 will not be heard.

Assuming local trunk E to be idle, the operator inserts plug 30 into ack 31. The trunk circuit E being a local trunk has a low resistance sleeve. A circuit now exists extending from grounded battery, through the winding 7 of relay 36, winding of relay 37, sleeve contacts of plug 30 and iack 31. to ground through the winding of sleeve relay 38. Relays 38. 37 and marginal relay 36 operate in this circuit. Relay 37 establishes an obvious circuit for relay 33 which on energizing disconnects the busy test relay 32 from the tip of the calling end of the cord and renders the tip conductor continuous at that: point. At its lower armature. relay 33 performs no useful function at this time. In attracting its outer left hand armature, relay 36 also establishes an energizing circuit for relays and 23 so that the condition of the cord is now under control of both the answering and calling ends of the cord. In attracting its inner left hand and righthand arniatures. relay 3 disconnects the left hand winding of relay tit; from bridged relationship with the calling end of the cord. The above mentioned armatures of relay 36 in closing their alternate contacts, connect battery and ground to the right hand winding of repeating coil 19. the latte-" being supplied bv war of the winding of relay 39, which relay corresponds to llt I bncli menace relay 1%: in the answering); end of the cord circuit. Relay 96 operates in series with lamp 53 in a circuit extending from grounded battery, through the filament of lamp 53. conductor 89, back contact and armature of relay 75, right hand winding of relay 96 front contact and cute left hand armature of relay to ground over the front contact and armature of relay 37. The lamp 53 lights in this circuit since relay 39 is not operated at this time as will appear from the following description. 7 Relay 38 operating" over the sleeve circuit establishes an obvious circuit for slow-releasing relay 41. hen the plug 30 is fully inserted in jack 31, relay 42 immediately operates over the ringside of the connection to grounded battery, through w' idingr of relay 39. Belay 39 may momentarily energize in this circuit. but will be immediately released when relay 42 operates since in operating, relay 42 dis connects itself from the ring side of the trunk and locks itself to grounded battery on the armature and front contact of relay 4]. "lelay 42 at its outer left hand armature, connects cut-oil relay 43 to the ring side of the tn 1.: but this relay does not operate at this time. At its inner right hand armature,- relay 42 causes the pulsing: relay 44 to operate in a circuit extending from grounded battery, through the winding; of relay 44, upper normal contacts of relay 43, to ground over the front contact and inner right hand armature of relay Relay 44 in operating. ts retardation coil. 51 and the wind I: polar relay 45 across the mechanical switching end of the trunl; E to prepare the selector S for ste ipin a At its outer armarelay connects a protective bridge, including conduiscr 40 and resista ce element 46. acr the pulsing contacts of re l 1 7 42. The trunk circuit is now in condito receive dial pulses. The operator non actuates the dialing; key and dials the required digits. The actu ation of this key connects the tip and ring conch tors of the calling end of the cord t to the conductors and. 48 respecrnr. In dialing the dial off-normal con- 3; is operated and cut-off relay 43 becomes chi-r sed in a circuit which may be traced from grounded battery. armature and front contact of relay 41. winding of relay 4%, contact and armature of relay 47, outer left hand arn'iatiu'e and front contact of rela 42, ring contacts of jack 31 and plueySO, lower alternate contacts of key 40, conductor 45%. 1 l; contact and left hand armature of relay 4-9, olf-nori al contact 93 of dial Q, hack contact and i. .er left hand armature of relay to around over the outer right hand armature and back contact of relay 50. Cutoff relay 4 -1 o iierates in this circuit and at its outer upper and lot 1' arinatures disconnects the mam -al end from the mechanical switching end of the trunk. At its inner upper armature, relay connects pulsing; relay 44 to the tip conductor of the manual end of the trunk thereby placing it in position to receive the dial pulses. Owing to the make-before lireal: contacts of relay 48, relay 44 remains energized during; its transfer to the tip conductor of the trunk. At its inner lower armature, relay 43 opens the circuit for relay 47 to ground at relay 45 and thus prevents it from being operated from the tip side of the connection. The operator now releases the dial so that the dial in returning to normal interrupts the pulsing cont-acts of the dial Q a predetermined number of times. The successive opening and closingof the pulsing contacts of the dial Q; interrupts the circuit for pulsing; relay 44 so that it follows the interruptions of the dial and causes the opening and closing of the brida'e across the mechanical switclr inn" end of the trunk which causes selector S to operate in a. manner well known in the art. For a complete disclosure of an automatic system in which selectors are thus operated, reference may be had to Reissue Pat ent N0. 13 901. F. Newforth. in, April 13. 1915.

Between operations of the dial and after the dial returns to normal. cut-oil relay releases restoringthe circuit to its condition prior to the actuation of relay 48. Relay 44 remains energized over its original energizing circuit.

In order to simplify the description and since a complete description of the operation of such selectors and connectors as S 1111C C may be had from the above mentioned patent it will be assumed that the line asso ciated with station P has been seized and that the subscribers thcreat signalled in the manner fully described in the above nientioned patent.

In response to" the actuation of the substation hell, the called subscriber removes the receiver from the switchhook whereupon relay 1-53 of connector C is actuated. The operation of this relay reverses battery and ground back over the connection so that polar relay 45 operates to connect relay 4'? across the tip and ring; of the manual end of the trunk E. It will he understood that where the connection was established the current through the windings of relay 4: was of such a direction as to prevent its operation at that time. A circuit now exists which may be traced from grounded battery through the winding of relay 39. front cont-act and right hand armature of relay 36. lower right hand winding' of repeating, coil 19, front contact and inner armature of relay 22, lower normal contacts of keys 92, 52 and 40, ring contacts of plug 30 and jaclr 31, conductor 85, contact and armature of relay 4 back contact and inner lower iiirinature of relay 43, wiigiding of relay 4'? tip contacts of jack 31 and plug 30, upper alternate contacts of relay 33, upper normal contacts of keys 40, 52 and 92, outer armature and front contact of relay 22, upper right hand winding of repeating coil 19, inner left hand armature and front contact of relay 36 to ground. Relay 39 operates connection between the calling end and the answering end so that should the operator tail to restore the dialing key and the called party had responded, there would be no talking connection set up so that conversation would be impossible. To avoid such a condition, applicant has provided an arrangement whereby the operator is given an audible warning signal should she fail to restore the dialing key. Assuming that the dialing key is actuated and that relay has operated in response to the current reversal caused by the response of the called subscriber, a circuit may be traced from grounded battery, winding of relay 29, back contact and inner right hand armature of relay 49, elf-normal contact 181 of dial Q, left hand armature and back contact of re lay 49, conductor 48, lower alternate contact of key 40, ring contacts ofplug 30 and jack 31, conductor 85, contact and armature out polar relay 45, back contact and armature of relay 43, winding of relay 47, tip

7 contacts of jack 31, and plug 30, upper normalcontacts of relay 33, upper alternate. contacts of key 40, conductor 95, pulsing contact 54 of dial Q to ground over the outer right hand armature and back contact of relay 50. Relays 4? and 29 operate in this circuit. Relay 4? performs the same "function as hereinbetore described. Relay 29 in operating connects a tone signal source 30 to the operators headset. ()n hearing this si nal the operator knows that the b called party has responded and that she has tailed to restore the dial key. She will thereupon restore the key, releasing relay 29, cutting oil the tone signal and conditioning the cord circuit tor talking par see. At the-termination of the (onversation, the called party hangs up the receiver whereupon relay 153 releases restoring the origi nal condition ofbattery and ground to the connection so that polar relay 45 again attracts its armature, this time in the opposite ",eeaeae direction thereby o iiening the bridge includ ing relay 47 across the manual end of the trunk. The opening of this bridge releases relay 39 whereupon the shunt is removed from lamp 53 and it is again illuminated indicating to the operator that the conversation has ceased and that she may proceed to take down the connection. Should the calling subscriber at station A restore the receiver before the plug 13 is removed from jack 14, relay 18 would be released and lamp 20 would thereupon be illuminated.

lVhen the operator removes plug 30 from jack 31, relay 38 releases which in turn rcleases relay 41. ltelay 41 in releasing, opens the locking circuit for relay 42 which thereupon restores its armatures releasing relay 44 and cutting off the protective bridge. Relay 44 in releasing, opens up the holding bridge to the automatic end of the connection. whereupon the switches restore in the well known manner. The removal of plug 13 from jack 14 releases relays 11, n; and 15. Relay 11 reconnects the line relay 10 to the line A, whereas relay 15 opens up the energizing circuits for relays 22, 23, 18 and 21, which thereupon releases restoring the circuit to normal condition. i

If the operator at any time during the period of conversation desires to listen in on the connection, she actuates the monitoring key M, whereupon a circuit is established extending from grounded battery through the winding of relay 25, conductor 26. to ground over the upper alternate contacts of key M. At its other contacts, key M connects the conductors 2S and 27 to the tip and ring conductors of the cord circuit, these conductors being normally associated with the operators telephone set by way of the hack contacts and armatures of relay 29. Relay 25, operating in the circuit just described, disconnects the operators transmit ling circuit from her receiver, and connects the receiver directly to the arn'iaturcs oi rclay 29. The operation of relay 25, therefore, disconnects the operators transmitting circuit from the receiving circuit and connects the receiving circuit directly across the talking conductors of the established connection. In this manner, the operator may listen in on the connection without disturbing the talking parties.

Referring now to the establishment of a. toll switching connection, which includes Figs. 1, 2. 4 and \Vith l ig. -t placed botween Figs. 1 and 5 and Fig. immediately above Fig. 1. the operation is as follows:--

Assuming that the call originates at the magneto station B. the subscriber thereat rc moves the receiver from the switchhook and actuates the magneto to send out current over the line loop in order to actuate the drop or line signal (30. Upon noting the actuated'dr'op, the operator insert-s plug 13 into jack and operates her talking key T. The calling line being of the magneto-type, has a rel 'icly high resistance sleeve. Upon ertion of plug 13 into jack 59, drop 60 is ren'ioyral from the line and .a circuit is esl .d which may as traced from ground y, through the winding of relay 15, j of relay l6, sleeve contacts of plug "ach 59 to ground. Owing to the l'iigh resistance sleeve of the magneto line B marginal relay 15 does not operate in this Relay 16, however, does operate but no useful function at this time. W7 is now ln'idged across the repeating coil it and is employed for supervisory pun po es as will hereinafter appear. Lamp 20 does not light at this time.

l he actuation of talking key T performs the same function as described in the previous connection, that is, to connect the operat ons telephone set with the calling line. The operator now converses with the calling subscriber in order .to ascertain the number of the desired line. Upon learning that a connection is desired with the party located at station R, the operator tests for a busy toll switching trunk in the saine manner as described in the testing for an idle local trunk. Assuming the trunk, Fig. 41,.to be an idle toll switching trunk the operator inserts plug 30 into jack 61 whereupon a circuit is established which may be traced from grounded battery, Winding of relay 36, winding of relay 37, sleeve contacts of plug 30 and jack 61 to ground Ithrou 'h the winding of high resistance relay Relay 36 being marginal does not operate in this circuit. Relays 37 and 62,11owever, operate,the former, establishing an obvious circuit for relay 33 and connecting ground to the middle alternate contact of dial key 40, by way of the outer left (hand armature and baclrcontact of relay Relay in operating, disconnects the busy test relay from the tip of the calling cord and renders the tip conductor of the cord continuous at that point. The operation of relay 62perforn'1s no innnediate function. A circuit may now be traced from grounded battery, through high resistance element 79, tl'irough the left hand winding of relay 65, back contact and outer lower arn'iature of relay 69, ring contacts of jack 61 and plug 30, lower normal contacts of keys 40, 52 and 92, inner a niature andback contact of relay 22, lower left hand windingof repeating coil 19, winding of marginal relay 75, upper left hand winding of repeating coil 19, back contact and outer armature of relay 22, upper normal contacts of keys 92, Maud l0, upper alternate contacts of relay iii-5, tip contacts of plug 30 and jack 61, upper inner normal contacts of relay 69' to ground through marginal relay 64-. Owing to the inclusion of resistance element 79 in this circuit, marginal relays 64 and '75 do not 01 erate. Relay 65, however, operates and in attracting its armature establishes a bridge for the mechanical switching end of the trunk, which prepares the selector switch D for stepping. This bridge may be traced from conductor 83, winding of relay 70, enter armature and back contact of relay 71, Sight hand winding of relay 65, back contact and outer right hand armature of relay 68, arn'iature and front contact of relay 65, windings of polar relay 63, front contact and inner armature of relay 62, to conductor 8 1 The operator now actuates the dial a0 whereupon a circuit is established which may be traced from grounded battery, through the winding of relay 49, conductor 88, middle alternate contact of key 40, back contact and outer left hand armature of relay 36, to ground over the front contact and armature of relay 37. Relay 49 operates in this circuit and in attracting its armature connects ground to the off-normal spring of dial Q, opens the circuit for relay 29, connects ground to the ring side of the cord and tabli's ies an obvious circuit for relay ()0. Relay 50 operates and at its outer right hand armature and front contact substitutes battery for the ground normally connected to the pulsing contact of dial Q. The re ,sistance of the tip circuit is now such as to permit relay 64 ,to operate in a circuit extend-- ing from grounded battery, front contact and outer right hand armature of relay 5t pulsing contact 54 of dial Q, conductor 95, upper alternate contacts of dial key 40, upper alternate contacts of relay 33, tip contactsof plug 30 and jack 61, upper inner normal contacts of relay 69, to ground through the winding of relay 64E. Relay 64 operates in this circuit and in attracting its left hand armature connects relay across the mechanical end of the toll switching trunk in parallel with the right hand winding of relay 65 and'windings of relay 63. In attracting its right hand-armature, rclay 6-l causes relay 6? to operate in a -'.rcuit extending from grounded battery, inner armature and back contact of relay '51. right hand armature and front contact of relay 64 back contact and outer left hand armature of relay 6?, winding of slow-release relay 67, to ground over lower inner normal contacts of relay 69. Relay 67 in opcrating, establishes a circuit for relay which may be traced from grounded battery, winding of relay 68, armature and front contact of relay 67, middle armature and front contact of relay 62 to ground. Relay 68 in at racting its inner left hand armature locks itself to ground on the middle armature of relay 62. At its outer left hand armature, relay 68 transfers the wind ing ,of relay 67 from the-hack contact to (1 ing up during this transfer. .peri'orins' no other function at this time.

front contact, slow-to-release relay 67 hold- Relay 68 Q. which in returning to normal interrupts the circuit of the impulse relay (it which, at itsleft hand armature opens the bridge including the winding of relay 70, thereby op erating relay ri a number of times correspomiling to the first digit of the desired number. Relay (57 being slow-to-release, holds up during the operations of relay (Set.

Since the operations of the automatic switches schematically represented at D, H and K do not enter into the present invention it is believed unnecessary to enter into a detailed description of these operations in this application' A complete description of the operations of such switches may be had by referring to a copending application. of R. L. Stokely, Serial No. 412,795, filed September 25, 1920. It will suffice to say that these switches are controlled by the succeeding digits sent out by the operator to connect the terminals of the toll switching trunk with the terminals of the desired line, in a manner fully described in the above mentioned copending application.

After the transmission of all digits, relay 65 remains operatedover the ring side of the connection to ground in the dialing equipment, or if the dialing key is restored to normal, as will be the usual condition, over the cord circuit bridge including the Winding-of relay T5. The release of the dial key removes the dialing equipment from the cord and renders the talking conductors of the cord circuit electrically continuous.

in accordance with general practice, and as described in the above mentioned copending application, the seizure of an idle line B will effect the reversal of current over the trunk N, whereupon polarized relay 63 responds. Relay (33 in operating, causes relay.

(it) to operate in an obvious circuit. Relay (3!) in attracting its armatures, disconnects relays (34: and 65 from across the tip and ring conductors of the trunk, opens the energizing circuit for relay 67, extends the tip and ring conductors of the trunk to the automatic switches and locks itself to ground by way oi the inner right hand armature of relay 68. By removing relays 6i and and high resistance 7 9 from across the trunk conductors, battery and ground are also reins /$256 moved so that marginal relay 75, which is bridged across the cord circuit, may now op crate in a circuit including grounded battery, left hand winding of relay A5, right hand alternate contacts of relay F-l, conductor 83, inner upper alternate contacts of relay 69, tip contacts of jack 6i and plug 30, upper alternate contacts of relay 33, up per normal contacts of keys e0, and 92, outer armature and back contact of relay 22, upper left hand winding of repeating coil 19, winding of relay 75, lower left hand winding of repeating coil 19, back contact. and inner armature of relay 22, lower normal contacts of keys 9:2, 52 and 40, ring contacts of plug 30 and jack 61, outer lower armature and front contact of relay (it), conductor 84 left hand alternate contacts of relay A5 and ground at the right hand winding of relay A5. Relay 75, owing to the low resistance of the circuit just traced, operates and establishes an obvious circuit for lamp 53. The illumination of lamp 53 at this time serves as a. ringing signal to the operator. The operator upon noting this signal actuates the ringing key 52 to signal the called subscriber in a manner fully described in the above mentioned copending application. When the called subscriber answers, the ringing current is ardematically disconnected from the line in the well known manner. The removal of the receiver at the called station R also causes supervisory relay 7 5, which corresponds to relay B43 of the above mentioned copending application, to be released in the same manner as described in that application in connection with the release of relay B't3. Relay 7 5 upon deenergizing extinguishes the lamp 53. At the termination of the conversation, the restoration of the receiver at station R causes relay to operate and energize the lamp as a disconnect signal. The operator upon noting the illumination of lamp 5:; may proceed to take down the connection. A disconnect signal may also be given by the calling subscriber in actuating the magneto associated with the station B. Current from the n'iagnclo causes relay 17 which is bridged across the answering end of the cord circuit to operate, establishing an energizing circuit for relay 21. Relay 21 operates establishing a locking circuit for itself and an energizing circuit for lamp 20 which may be traced from grounded battery, through the filament of lamp 20, left hand winding of relay 21, front contact and armature of relay 21, front contact and armature of relay 16, to ground over the upper normal contacts of talking key T. The operator may extinguish the lamp 20 by actuating her talking key T or by with drawing plug l3 from jack 59. The actuation of the magneto in the manner just descril'ied may also serve as a recall sigill! operator causes relay '16 to release, this lay being the onlyrelay,operatedlat this nal -to the operator who then iactuates the said equipment to tunction with the talking hey T to associate her telephone set with tliccaflli g line i n-order to ascertain the desires of the calling subscriber.

The operator takes \down the eonneotion by removing plugs and 1-3 .from jacks 61 and 59, respectively. The remo ual of plug 30 fromjac'k 61 causes relays 62 :and 37 to release. Relay 62 .in releasing, opens the locking circuit for relay 68 which in turn releases and opens the lockingcircuit for relay 69 restoring the trunlrcircuit to normal. The automatic switches are released :in the usual manner as described in :detail in the above mentioned copending application.

When removing plug 13 vi roni jack 5%.), the

I tue.

The operatormay listen-iirduring the period of conversation in the san1e. 1nanner as described inconnection with the decal connection.

hat is claimed is: 1. In a telephone system, a plurality o trunk circuits havingi'different dialing char acteristics, a cord circuit, a dial circuit for supplying different dialing potentials, a key for connecting the dial circuit to the cord, and means operative in response to the con nection of said cord circuit with one of said trunk circuits and the actuation of said key for conditioning said dial circuit to supply the particular dialing potential required for the trunk circuit taken for use.

2. In a telephone system, a plurality of trunk circuits requiring different potentials for dialing thereover, a cord circuit, the dialing circuit associated therewith for supplying diiferent dialing potentials, and means effective subsequent to the association of said cord circuit with any of said trunk circuits for selecting at said dialing circuit the potential required by the trunk circuit employed.

3. In a telephone system, a plurality of trunk circuits, a relay for each of said trunk circuits, each relay requiring a different connection of current to effect its operation, a cord circuit, a dial, a battery and circuits therefor for connecting said battery through one pole or the other to said dial, and means operative in response to the association of said cord circuit and said dial with any of said trunk circuits for selecting the proper pole of the battery to cause the operation of the relay associated with the trunk circuit employed.

4:. In a telephone system, a cord circuit adapted to function with a plurality of trunk circuits, 'each of said trunk circuits requiring a different polarity for dialing thereover, dialing equipment, and discriminating means associated with said cord circuit and respon' 'sive to the association of said cord with any oi" said trunk circuits for conditioning trunk circuit employed.

,5. In a telephone system, a local trunk, a ll sw t h ng t unk, a dialing circuit adapted to fiunct-ion in a di,if erent manner withieach of said trunks, aeord circ and means associated with said cord CllIe 1i" discriminating between said local and itoll switching trunks {to condition said dial cii cult to fiu ction therewith.

sponsive on the connection of the dialing circuit with any trunk circuit to cause the polarity required ineach case to be supplied by the dialing circuit. 7

l7- in combination, :a dialcircuit adapted to supply different polarities fordialing, a

cord circuit associated therewith, dii lerent types of connecting trunks for association with said dial circuitthroughsaid-cord circuit and .=1 neans associated with said icordcircuit responsive to the connection of the cord circuit with a trunk to cause the polarity required in each case to be supplied by the dial circuit.

8. In combination, a dial circuit adapted to supply different potentials for dialing over different connections, a cord circuit, and a marginal relay associated with said cord circuit for discriminating between the different connections to supply the required potential.

9. In a telephone system, a subscribers station, a connection thereto including a cord circuit and a plurality of connecting links, a dial circuit, an operators receiver associated therewith, means for associating said dial circuit with said cord, and means responsive to the removal of the receiver at said station and the operation of said first means for connecting a source of current to said receiver..

10. In a telephone system, a substation, a connection thereto including a cord cir cuit and a plurality of connecting links, a dial circuit, an operators headset, means for associating said dial circuit with said 7 cord, a source of tone current, and means responsive to the removal of the receiver at said station and the operation of said first means for connecting said tone current to said headset.

11. In a telephone system, subscriber stations, a connection between two subscriber stations including a cord circuit and a plurality of connecting links, an operators position, means for splitting said cord circuit during and after the establishment of said connection, and means responsive to the removal of the receiver at one of the stations in the connection for indicating to an operator at said position the split condition of said cord circuit.

12. In a telephone system, subscriber stations, a connect-ion between two subscriber stations including a cord circuit and a plurality of connecting links, an operators position, means for splitting said cord circuit during and after the establishment of said connection, signaling means, and means responsive to the removal of the receiver at one of the stations in the connection for operating said signaling means thereby indicating to an operator at said position the split condition of said cord.

13. In a telephone system, a subscribers station, aeonnection thereto including a cord circuit and a plurality of connecting links, an operators receiver, a source of tone current, means for splitting said cord circuit during the establishment of said con nection, and means responsive to the removal of the receiver at said station for connecting said tone current with said operators receiver to indicate to the operator the split condition of said cord circuit.

14. In a telephone system, substations, a connection between two substations including a cord circuit and a plurality olf con-- necting links, an operators position, means for splitting said cord circuit during and after the establishment of said connection, and means controlled from one of the substations in the connection for indicating to an operator at said position the split condition of said cord circuit.

15. In a telephone system, a substation, a connection thereto including a cord circuit and a trunk circuit, a pulsing relay for said trunk circuit, a dial, a dial key, means operative over the ring side of said trunk for energizing said relay, and means responsive to the oil-normal actuation oi. said dial subsequent to the operation of said key for connecting the relay to the tip side oi said trunk.

In Witness whereof, I hereunto subscribe my name this 17th day of August A. 1)., 1923.

CLARENCE B. FOVV I; Eli. 

